1. Field of the Technology
The present technology relates to an optical fixing device and an image forming apparatus.
2. Description of the Related Art
An electrophotographic image forming apparatus such as a copier, a printer or a facsimile is provided with a fixing device for heating, melting and fixing an unfixed toner image formed on a recording medium such as a recording sheet. As an example of the fixing device, Japanese Unexamined Patent Publication JP-A 11-38802 (1999) discloses a roller-pair type fixing device comprising a fixing roller and a pressure roller.
The fixing roller is a roller member having an elastic layer formed on the surface of a hollow metal core made of metal such as aluminum, and a heat source such as a halogen lamp is arranged inside the metal core. The temperature on the surface of the fixing roller is controlled by a temperature control device which turns on/off the halogen lamp, and temperature control is performed based on a signal that is outputted from a temperature sensor disposed on the surface of the fixing roller. The pressure roller is a roller member having a heat-resistant elastic layer such as silicone rubber disposed on the surface of the metal core. Such a pressure roller is in pressure-contact with a peripheral face of the fixing roller, and a nip region is formed between the fixing roller and the pressure roller due to elastic deformation of the heat-resistant elastic layer.
In such a fixing device, a recording medium on which an unfixed toner image is formed is held in the nip region between the fixing roller and the pressure roller, and both these rollers are rotated, thereby conveying the recording medium, as well as melting and fixing the toner image on the recording medium by heat of the peripheral face of the fixing roller.
In the roller-pair type fixing device, however, the fixing roller and the pressure roller at room temperature are needed to be increased to a predetermined temperature after supplying power, and thus required to have a warm-up period. Moreover, in a standby state where image formation is not performed, the surface of the roller is needed to be kept at the predetermined temperature, and thus must be heated all the time even at the standby period. As a result, there is a problem such that unnecessary energy is consumed at times other than image formation.
In order to solve such a problem, Japanese Unexamined Patent Publication JP-A 7-191560 (1995) discloses a laser fixing device for condensing laser beams emitted from a plurality of laser devices on a recording medium, thereby fixing an unfixed toner image. In such a laser fixing device, the laser beams emitted from the plurality of laser devices are condensed on the recording medium, and the laser beams with increased light intensity are irradiated to an unfixed toner image on the recording medium, thus making it possible to improve fixability.
However, in the laser fixing device disclosed in JP-A 7-191560, the unfixed toner image on the recording medium is fixed only with heat caused by irradiation of a laser beam, and an image on the recording medium formed after fixing has thus no sufficiently high fix level as well as no sufficiently high smoothness and a gloss level.